The Trow Point Bed—a deposit of Upper Permian marine oncoids, peloids and columnar stromatolites in the Zechstein of NE England

Abstract

SUM M A R Y:An extensive thin bed of oncoids, peloids and columnar stromatolites occurs at the top of the Cycle 1 carbonate of the English Zechstein sequence in NE England; here termed the Trow Point Bed, it lies on the lower part of the basin-margin slope, basinward of a linear shelf-edge reef in the Ford Formation. The bed is generally 0.05 0.20 m thick but locally ranges to 0.60 m; it rests on an uneven surface that has a local relief of up to 15 m and slopes exceeding 35 ~ in places. It contains a sparse marine fauna of foraminifera, ostracods and bivalves; there are only a few traces of current action and sorting, and terrigenous sediment nowhere comprises more than 2% of the bed.The Trow Point Bed is generally similar to deposits described at a comparable stratigraphical position in Germany and Poland and although environmental indications are partly mutually contradictory, it seems likely that the bed accumulated in oxic conditions on the basin floor under water perhaps 25 100 m deep. FIG. 4. Typical packstone facies of the Trow Point Bed, showing a range of grain types. (a) Lower part of bed, depth 263.60 m, borehole D4 (NGR NZ 5000 5201). British Geological Survey thin-section E 54516. Scale 2 mm. (b) Middle of bed, mid-north side of Frenchman's Bay, South Shields (NGR NZ 3889 6617); E 54517. Scale 1 ram. (c) Compressed oncoids and lithoclasts near top of Trow Point Bed. Scale 0.5 cm. Offshore Borehole 12, depth 269.75 m (NGR NZ 4993 4896). Sunderland Museum specimen TWCMS D408.4. Photograph by T. Pettigrew. (d) Stylolitic contacts between grains in Trow Point Bed. Scale 1 cm. Offshore Borehole 1, depth 311.05 m (NGR NZ 5333 4043).

Emplacement and diagenesis of gypsum and anhydrite in the late Permian Raisby Formation, north-east England

“…2). Basinwards of the reef, but not necessarily coeval with it, is a thin but persistent unit of oncoids, peloids and columnar stromatolites called the Trow Point Bed (Smith 1986) (Fig. 2).…”

Stratigraphy of the Lower Werra Cycle (Z1) in West Germany (preliminary results)

“…In the English part of the Zechstein basin there is a very clear partition of the first cycle shelf carbonate into a lower and an upper member (Smith 1968(Smith , 1980Smith et al 1974), but in West Germany there are only local formations in the marginal and swell areas; only tentative attempts have previously been made to correlate these local formations.…”

“…These changes probably affected the whole basin and therefore may have been caused by eustatic movements rather than local tectonic events (Smith 1980). As the changes in the sea-level were apparently very rapid in comparison with the rate of sedimentation, it is possible to subdivide the Zechstein Limestone independently of facies and also to correlate these subcycles throughout the basin.…”

Upper Permian Main Dolomite microbial carbonates as potential source rocks for hydrocarbons (W Poland)

“…In the SPB microbial carbonates are mostly known from basin and platform facies of the PZ1 Zechstein Limestone (Ca1) and PZ3 Platy Dolomite (Ca3) carbonate cycles (e.g. Kerkmann, 1969;Peryt and Pią tkowski, 1977;Füchtbauer, 1980;Paul, 1980;Smith, 1986;Gą siewicz et al, 1987). In the case of the Ca2, the data on microbial facies which coexisted with algal communities is rather scarce.…”